Seat belt units installed in vehicle seats in automobiles and the like have been used for restraining occupants with seat belts in the units in emergency situations such as collisions in which a large deceleration acts on the vehicles. Among such seat belt units, those supported by pillars of vehicle bodies and including belt guide anchors that guide seat belts such that the seat belts are slidable, for example, have been discussed in, for example, Japanese Unexamined Patent Application Publication No. 2002-200964.
According to a belt guide anchor described in Japanese Unexamined Patent Application Publication No. 2002-200964, a seat belt drawn from a seat belt retractor is folded back at the belt guide anchor and guided to a shoulder of an occupant so as to be fitted to the occupant. With this, the seat belt can restrain the occupant at a correct position.
In some cases, seat belt retractors in seat belt units need to be disposed far rearward of occupants depending on layouts of vehicles. When the seat belt retractors are disposed at rear positions in this manner, belt opening angles between portions of seat belts before being folded at belt guide anchors (i.e., portions adjacent to the seat belt retractors) and portions of the seat belts after being folded at the belt guide anchors (i.e., portions adjacent to the occupants) become large.
However, in the belt guide anchor described in Japanese Unexamined Patent Application Publication No. 2002-200964, molded resin portions adjoining a belt insertion hole are made thick, and project in the thickness direction of the belt guide anchor (inward and outward directions at a side of a vehicle) by a large amount. These expanded portions can increase the radii of curvature of the molded resin portions adjoining the belt insertion hole such that a seat belt can be smoothly slid at these portions.
When the expanded portions are formed in the vicinity of the belt insertion hole in this manner and the belt opening angle between the portion of the seat belt adjacent to the seat belt retractor and that adjacent to an occupant is increased as described above, the seat belt is pressed into contact with these expanded portions. Therefore, friction between the seat belt and the expanded portions of the belt guide anchor when the seat belt is drawn out is increased, and the seat belt cannot be smoothly drawn out. Furthermore, the belt guide anchor can be rotated by the frictional force, and an offset (jamming) of the seat belt can occur more easily. Accordingly, when the seat belt retractor is disposed in a vehicle in the above-described layout, the handling operability of the seat belt can be impaired.
Degradation of the operability of the seat belt can be prevented by increasing the width of the belt insertion hole of the belt guide anchor. However, when the width of the belt insertion hole is increased, the movement of the seat belt cannot be regulated in the width direction. Thus, the offset can easily occur in a similar manner.